DC motors are usually controlled by a motor control circuit known as a motor controller. One conventional motor controller receives an input voltage from a preset reference source external of the motor, as an input command signal. The motor controller provides the necessary output command voltage to the motor. The DC motor may have an integral generator winding which acts as a tachometer. Based on how fast the motor is rotating, the generator winding supplies a voltage back to the controller as a direct feedback. The controller then compares the feedback voltage to the preset input command voltage and uses the output command voltage to adjust the motor speed until equal values of feedback voltage and preset input voltage are obtained, if possible.
It has been found that the motor speed control in the aforesaid system is often inaccurate and that speed drift can affect system performance.
It is, therefore, an object of the present invention to provide a system for controlling the motor speed more accurately than the basic system described above.
Another object of the present invention is to provide a system for controlling the speed of a motor, which is relatively simple in operation and easy to manufacture.
Other objects and advantages of the present invention will become apparent as the description proceeds.